Monitor probe for high-frequency transmission lines



May 28, 1946. G. L. ussELMAN 2,401,205

MONITOR PROBE FOR HIGH FREQUENCY TRANSMISSION LINES Filed Nov. 21, 1941 2 Sheets-Sheet 1 INVENTOR A'IITORNEY y 1,946. s. L. USSELMAN MONITOR PROBE FOR HIGH FREQUENCY TRANSMISSION LINES Filed Nov. 21, 1941 2 Sheets-Sheet 2 OR' I dis m 'INVENT 6204 945. V

ATTORNEY Patented May 28, 1946 MONITOR PROBEFOR HIGH-FREQUEN CY TRANSMISSION LINES George L. Usselman, Port Jefferson, N. Y., assignor to Radio Corporatio tion of Delaware 11 oi. America, a corpora- Application November 21, 1941, Serial No. 419,977 2 Claims. (01. us -44) This invention relates to a novel and useful device for picking up a small amount'of radio frequency power for monitoring purposes, from an ultra-high frequency circuit.

An object of this invention isto provide a simple and emcient monitor pickup probe fora coaxial line.

Another object of this invention provides a pickup probe for a gas or fluid-tight transmission line.

be exercised to provide a suitable radio frequency pickup device without allowing the gas or fluid to escape. This invention provides an 3 improved adjustable insulated gas-tight pickup probe to meet the rigid requirements.

This invention will best be understood by re ierring to the accompanying drawings, in which: Fig. 1 is a plan view with the cover removed of the pickup probe oi tins invention:

Fig. 2 is an elevational view partly in section I of Fig. 1; and

Fig. 3 is another elevational view partly in section showing the shieid and low power coaxial line connected thereto.

Referring now in detail to the drawings, a fiange shaped metallic housing i is provided with an upper inwardly extending rim portion la. The lower portion is threaded at lb to receive a threaded clamp ring l! which is slotted at to for rotation in threads lb. insulating base 3 of "Mlcalex for closing oii one end of the housing is forced against rim to which is slotted to receive a packing ring 3a. The insulating disc 3 is secured in place by means of clamp ring 2. A thin spring washer 4 of beryllium copper is interposed between the undersurface of base 3 and clamp ring I to insure pressure on packing ring In. A central brass hollow supportmember 5 is provided with internal and external threads. A threaded stud 8 is slotted at to so that it may be freely screwed up and down within member 5. A spherical sector I is fastened to the lower end of stud I and serves as the. capacitive electrode for picking up the desired amount oi voltage from the inner conductor 8 oi the coaxial line. Member I is provided with a packing groove 5a in which packing material is provided to prevent entry of any fluid to the outer portion of the device. Central support member. 5 isretained in place by a hexagonal nut 9, A terminal member II is fastened to member 5 by means of nut II. The external thread on member 5 is provided at the upper portion thereof with a knurled cap it, the cap i3 being made fluidtight by means of a gasket. A screw driver slot i5 is provided in the upper end of cap is. A support bracket or, sub-base i6 is soldered to the outer conductor II which is provided with an aperture l8 at any desired" point along the line where a pickup of the power is to be taken off. A ring-shaped packing member It to prevent loss of fluid is interposed between the top side of member l6 and is retained in a groove in the lower portion of flange l. Eight filister screws 2d securely clamp members i and it together. As shown in Fig. 3, the entire pickup probe of this invention is completely enclosed by a shielded metallic container 2i having a pivoted lid 22. An aperture 23 is located in the side of shield H for connecting the outer conductor 24 of the low power pickup line 25. In order that the entire assembly be made gas or fluid-tight, member 68 is securely soldered to the outer conductor ll, also, all surfaces which are joined together are provided with suitable gaskets.

In the operation of this device, lid 22 is moved to one side and knurled cap it is removed. A small insulated handle screw 'driver is passed through the aperture in member 5 to engage the slot 6a of screw 8. It will be noted that screw 6 is provided with a head which prevents memher i from coming in direct contact with the high voltage flowing in the inner conductor 8. The minimum adjustment between electrode 1 and the inner conductor 8 is approximately /5 the maximum adjustment being substantially /2". Screw 8 is elevated up and down until the proper pickup voltage is obtained in the grid circuit of an amplifier unit (not shown) which "is connected tothe pickup line 25, or if desired, line 28 may connect to the plate or grid circuit of a detector unit.

Probe electrode 1 may be of various sizes to give the proper pickup voltage. Electrode 1 and the aperture It in the outer conductor i! should be well rounded over and polished to prevent areover of the high voltage which normally exists in the circuit. The insulator I should be stron enough mechanically to resist the live gas pressure and the insulation qualities should have very low loss to prevent failure by heating which occurs in all such ultra-high frequenc circuits. Any suitable nuid'is pumped in between conductors 3 and This invention should not be limited to the pre. else arrangem nt shown.

ed is:

l. A gas tight pickup probe for an ultra high frequency coaxial line with inner and outer conductors, comprising a metallic fluid tight casing having an upper and lower portion, said lower portion secured in gas tight engagement to the outer conductor of said line, an insulating-member closing 015 one end of the lower portion of said casing, a fluid tight gasket interposed between said insulating member and the lower portion of said casing member, an adjustable capacitive electrode in the form of a spherical sector, a hollow threaded support member, a threaded electrode stud being threaded within said hollow threaded support member for adjusting said capacitive electrode, said threaded support memher being supported by said insulating member and sealed within the lower portion of said casing, said capacitive electrode located within said outer conductor and secured to an end or said threaded stud to be in capacitive relationship with the inner conductor of said'line, and a fluid tight cap arranged to cover the outer end of said hollow threaded support member.

2. A gas tight pickup probe for an ultra high frequency coaxial line with inner and outer conductors, comprising a metallic fluid tight casing having an upper and lower portion, said lower portion secured in gas tight engagement to the outer conductor oi. said line, a disc of insulating material closing of! one end of the lower portion of said casing, a fluid tight gasket interposed between said disc and the lower portion of said casing member, an adjustable capacitive electrode, a hollow threaded support member, a threaded electrode stud being threaded within said hollow threaded support member for adjusting said capacitive electrode, said threaded support member being supported by said insulating member and sealed within the lower portion of said casing, said capacitive electrode located within said outer conductor and secured to an end of said threaded stud to be in capacitive relationship with the inner conductor of said line. a metallic shield surrounding the hollow threaded support member, and a low power coaxial cable having its outer conductorioined and connected to said shield, and its inner conductor electrically connected to said hollow threaded support member.

GEORGE L. USSELMAN. 

